Blood test for weight loss: your GLP-1 baseline

Losing weight with GLP-1 medication changes a lot in your body at once: you eat less, your weight goes down and your metabolism adjusts. A baseline beforehand records how your values look now, so a later check has something to compare against.

Without a starting point, a result is harder to place. With a baseline blood test as your reference, you and a doctor can more easily see which values move along with your journey.

• People who are about to start a weight-loss injection and want to record a starting point
• People who have just begun semaglutide or tirzepatide and want to know their baseline values
• People who want their blood sugar, cholesterol, liver, kidneys and vitamins measured in one go
• People who want to arrange this without a referral

This blood test does not determine whether a weight-loss injection is suitable for you. That assessment always belongs with a doctor.

• Blood sugar and insulin: HbA1c, fasting glucose and fasting insulin.
• Cholesterol and fats: total cholesterol, HDL, triglycerides and ApoB.
• Liver: ALT, AST, bilirubin and albumin.
• Kidneys and minerals: creatinine, sodium and potassium.
• Thyroid: TSH.
• Pancreas: lipase.
• Nutrients: vitamin D, vitamin B12 and ferritin.

Your blood sugar and insulin values can offer insight into your metabolism before you start. Your cholesterol and triglyceride values can provide context around your heart and vascular health, and your liver and kidney values give a view of how those organs are doing at that moment.

Because a weight-loss injection can strongly reduce appetite, nutrients such as vitamin D, vitamin B12 and ferritin may be relevant to know as a starting value. Together these are a snapshot, not a diagnosis, that you can discuss with a doctor.

Blood is drawn at a certified collection point. In the Netherlands there are 700+ locations, which you choose yourself after ordering.

This is a blood test without a GP: you pick a location and a moment that suits you. The draw usually takes only a few minutes.

This baseline can be useful just before you begin a weight-loss injection, or in the first weeks after starting. That way you record your starting values at a moment when little has changed yet.

If you want to keep following your values over time, a later check fits well with this. Some people choose to test periodically to stay informed.

Your results appear with a reference range for each marker. Values outside that range are worth discussing with a doctor, who can place them in the context of your lifestyle, diet and weight-loss journey.

A single value outside the range does not immediately point to a problem. It is about the overall picture, and often about the change compared with your baseline.

Your results are usually in your personal dashboard within a few working days, with the measured values next to the reference ranges. You view them whenever it suits you.

Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.